David Hambling reports in Forbes:
Both sides use FPV ambush drones, called 'waiters.' The drones waits for a target, then strike. They are often uses to hit vehicles on supply routes to the front. Ambush drones are controlled by fiber optic cable spooled from the FPV, which are hard to cut. This has led to lasers. In drone piloting, "smoking the ESC" is burning out the Electronic Speed Controller which controls the motor. Excessive current causes the components burn out. But this latest development may be more advanced technology. A structured light scanner which analyses the distortion of the projected pattern to map the shape of objects below in 3D. An automated recognition system could pick up the shape of a parked drone. The drone is "fried" and inoperable.
A Russian drone waiting in ambush by the side of the road captures something weird advancing towards it, a ball of light in the sky beaming down a square of light which scans up and down the road. As the light passes the ambush drone, we see a “NO IMAGE” warning as the feed from the ambush drone is suddenly cut off.
The light certainly looks science fictional, leading X user BreacherFPV to dub it a “Strange alien road scanner.” Many commentators identify this as a drone with a laser weapon which cuts the ambush drone’s fiber optic cable. However, a closer look at the video shows something very different.
Both sides make extensive use of FPV ambush drones, also known as Waiters or “Zhdun.” The operator lands beside a road or on a building and waits for a target to appear, then takes off and strike from close range. They are often used to hit vehicles on supply routes to the front.
Ambush drones are typically controlled via a fiber optic cable spooled out from the FPV rather than radio. Unlike a radio connection, fiber is not limited by line-of-sight, so the operator can maintain good connection even when the drone is on the ground. And fiber uses less power than radio, so the drone can wait for several hours without draining the battery.
Fiber drones are so common that in some places the landscape is festooned with used fibers glittering in the sun like spider webs.
The best way to tackle ambush drones is to destroy them before they can attack. Ukrainian videos show bomber drones executing clearing missions, locating and bombing Russian ambush drones where they lie. There have also been many schemes to cut the fiber link, none of which seem to be practical so far. This has led to the idea that a laser weapon is slicing through the cable.
Technically this is not plausible. While Ukraine is on the early stages of deploying a counter-drone laser known as Tryzub this is a large and relatively low-power system.
Cutting glass with a laser is challenging although there are industrial lasers used for exactly this job. However these use invisible infra-red beams because visible light passes right through glass or reflects off it, and cutting needs to be with a different wavelength, not the visible light seen in this video.
A second suggestion is that the beam is getting into the fiber cable and disrupting the electronics. Again, this seems highly unlikely, largely from the physics involved. The fiber optic cable is tiny, and only a minute fraction of the projected light is captured.
Previous Ukrainian efforts to use laser in a similar way to disrupt or make visible fiber optic communications failed, as experiments with laser pointers showed.
“We tried this idea in the first week of searching for solutions against drones using optics,” wrote Ukrainian electronics warfare expert Serhii “Flash” Beskrestnov. “The idea DOES NOT WORK in practice.”
Finally, laser beams focus their power on a small area. They are not several feet across and square like the beam seen here.
So what is going on and what takes out the connection? The answer can be found by looking more closely at the video and in particular the numbers showing the drone’s condition.
“Smoking The ESC”
Looking at the video, you can see that the horizon shifts as the numbers start changing rapidly, as the operator attempts a rapid takeoff. The current indicator on the right of the screen goes from 0.3 A at rest before surging to over 112 A as the feed goes dead.
To experienced drone operators, this can only mean one thing.
“The pilot smoked the ESC trying to run away from the strange alien road scanner,” BreacherFPV writes on X. “Went from a stand still to yanking 80% throttle. That doesn't go well with a heavy drone.”
In drone piloting, "smoking the ESC" is burning out the Electronic Speed Controller which handles the motors. An electrical short or, in this case, excessive current, causes the components burn out with a puff of white smoke. The ESC is "fried" or destroyed, and the drone is inoperable. Other drone flyers concur that this is what the video shows,
The fiber optics were not cut or destroyed, but the drone was lost due to operator error. This still leaves the question of just what that thing was coming down the road that scared them so badly?
Sensing With Structured Light
Ukrainian drones carry out sweeps looking for FPVs along roads. At night ambushers may be visible from their thermal signature, though a drone with its engines off does not present much of a heat source.
The fiber optic cable is harder to hide though. Fiber cables glint in strong light, and a road which is in use should not have any old cables lying across it. Any glint on the road suggests a new arrival and an ambush drone nearby. What we may be seeing is a drone fitted with an LED searchlight like DJI’s Zenmuse S1, shining it up and down to catch the telltale glitter of a fiber cable.
But this may be more advanced technology. The square of light projected on to the road suggests a structured light scanner which analyses the distortion of the projected pattern to map the shape of objects below in 3D. This technique is sued for detailed drone surveys, and an automated recognition system could certainly pick up anything as distinctive in shape as a parked drone.
What is interesting is that rather than lying low, the Russian drone operator panics and lifts off in a hurry. They have seen, or been warned about the Alien Road Scanner before, and they know that if they leave the FPV there it will be destroyed soon afterwards.
The mystery remains. We can be fairly confident that this is not a high-energy laser weapon, but it does seem to be some sort of drone device for clearing roads. And in this case, there is one Russian FPV which will not be killing any Ukrainians.
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